308 Adventures in Scenery 



flank of the Sierra Nevada range; and not on the crest of the 

 range or in the valley at its foot; or in other regions surround- 

 ing, may not be so definitely answered. 



Gold is widely distributed, and occurs in rocks of all sedi- 

 mentary geologic formations of all ages. Yet here, in a compara- 

 tively narrow belt extending in a general way parallel with the 

 crest of the mountain ra'nge but along its lower flank only, dis- 

 continuing in a narrow strip at the south and thinning or ceas- 

 ing under deep beds of lava at the north, is a region which has 

 been one of the outstanding producing fields of the world. To 

 the lay reader as well as to the geologist the question why is 

 bound to arise. The only explanation that can be given in the 

 present state of knowledge of the geology of the earth lies in 

 what has been deciphered from a study of the rocks, the geo- 

 logic history and processes involved. 



Two Groups of Rocks in Gold Belt 



Briefly stated, two belts of old sedimentary rocks lie along 

 the lower flanks of the mountain range. These rocks are much 

 bent, folded, and crumpled, tilted sometimes to a nearly ver- 

 tical position. They were deposited as sea sediments, that is, 

 muds, sands and lime. In the disturbances of mountain build- 

 ing they have been baked and transformed (metamorphosed) , 

 and now appear as slates, quartzite, and marble (crystalline 

 limestone) . These rocks are a remnant of the ancient roof 

 rocks that were uplifted when the great batholith of molten 

 rock (now the granitic rocks of the Sierra Range) was forced 

 up under the sedimentary formations that had been laid down 

 during the long periods of Palaeozoic and Mesozoic time. That 

 they have been terrifically squeezed and compressed is shown 

 by the way the strata are now folded and crumpled. The geo- 

 logic complexity of these rocks is said to be greater than that 

 of any other equal area of the western Sierra slope. 



"The rocks that make up this belt of folded and crumpled 

 formations, this remnant of the ancient roof rocks of the Sierra 



